One person died after a shuttle boat carrying 50 people to a casino boat off Florida’s gulf coast caught fire on Sunday afternoon, forcing passengers to jump overboard to escape the fast-moving flames, the authorities said.

Flames consumed the boat around 4 p.m., but emergency workers had to wade into the frigid waters about 25 miles northwest of Tampa, Fla., to rescue about 15 people who had not made it ashore, the police said.

On Monday, Chief Gerard DeCanio of the Port Richey Police Department said that one passenger, a 42-year-old woman, had died. Her name and cause of death had not yet been released.

The woman had been taken to Regional Medical Center Bayonet Point in critical condition on Sunday and died at 10:42 p.m., the hospital spokesman, Kurt Conover, said on Monday. Beth Fifer, an assistant to the chief executive officer of the Tropical Breeze Casino, said on Monday that she had spoken to the family of the deceased woman but had no further information.

The Coast Guard is investigating the cause of the fire, Michael De Nyse, a Coast Guard spokesman, said in an interview on Monday.

About a dozen other people were treated for exposure, anxiety and other minor injuries, Chief DeCanio said on Sunday.

Chief DeCanio said on Sunday that quick thinking by the shuttle boat’s captain helped avoid a disaster. Shortly after the vessel left the dock, the captain spotted smoke spewing from the engine room and decided to turn around. But the fire rapidly grew, so the captain steered the boat toward the shore, allowing passengers to jump off into shallow water, Chief DeCanio said.

“Another quarter-mile out, this would have been a tragedy,” he said.

The Sun Cruz shuttle boat makes several trips daily from the city of Port Richey to a casino boat about three and a half miles offshore, in international waters where gambling is legal.

Photos and videos posted on social media showed big flames coming off the vessel and passengers swimming in the water. Chief DeCanio said the captain almost ran the boat aground as he tried to get close to the shore.